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FemaletimberRattlesnake(Crotalus horridus)(female-515inthisstudy)justafteremergencefromhibernation.

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associative behavior and affinity for anthropogenic Habitats in Two Relocated

Timber Rattlesnakesmindyl.Walker1,ericD.kadlec1,RyanD.miloshewski1,andGeorgeR.pisani2

1Departmentofbiology,RockhurstUniversity,kansasCity,missouri64110,UsA(mindy.Walker@Rockhurst.edu)2kansasbiologicalsurveyandecologicalReserves(ksb/ksR),lawrence,kansas66044,UsA

thetimberRattlesnake(Crotalus horridus)isconsideredtobeaspeciesInneedofConservation(sInC)inkansas(brown1993),which

affordstheanimalsandtheirhabitatminimalprotectionwheretheyoccur.populationsofthisspeciesoftenexistnearhumanpopulationcentersandhaveperhapsthemostinteractionwithhumansamongspeciesofCrotalus(Walkeretal.2009).Ineasternkansas,whichrepresentsthewesternextentofthespecies’geographicrange(Clarketal.2007),humanpopulationsfre-quentlyencroachonaggregationsites(hibernaculaandrookeries)oftheseanimalsandoftenoverlapwiththeirforagingandbreedingroutesduringthesnakes’activeseason(Fitch1999,pisaniandFitch2006,Fitchandpisani2006,edwardsandspiering2005).InsomewesternsuburbsofkansasCity,populationsofC. horridusutilizerecentlydevelopedareasasbothtran-sienthabitat(sensubrown1993)andsummerrange(Walkeretal.2009).

Walkeretal.(2009)describedmovementsovera2-yearperiodoftelemeteredtimberRattlesnakesstudiedaspartofaden-relocationeffort.InFebruary2007,theapproximately25-year-olddenontheoutskirtsoflenexa(kansas),composedofroadrubblecappedwith~1mofdirtfill,wasthreatenedwithimminentdestructiontopermitthedevelopmentofalargeretailcenter.thatstudyhadtwomajorgoals:(1)savethispopulationofsnakes,and(2)testanewmodelofconservationbyrelocation.previousstudiesonsmallernumbersofsnakesunderdifferentrelocationprotocolshadindicatedthatrelocationgenerallywasnotaviableconservationmethod. Achangeinthedevelopmentplansparedtheoriginaldensite,whichremainspartofalenexacitypark.notalltimberRattlesnakesutilizingthatdenhadbeencapturedduringtheoriginalrelocationeffort,andperiodicallysomesnakescausedpublicalarmbyutilizinghabitataroundhomes.on22

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Fig. 1.maleandfemaletimberRattlesnakes(Crotalus horridus)entangledinlandscapingfabric,July2009ataprivateresidenceinlenexa,kansas.thesesnakes(transmitterfrequencies105,515,respectively)weresubsequentlyrelocatedandtheirmovementstrackedbyradiotelemetry.thisphotographwastakenbythehomeowner.

236 IRCFReptIles&AmphIbIAns•Vol18,no4•DeC2011

April2009,twofemaletimberRattlesnakeswerecapturedseparatelyafteremergencefromtheden,equippedwithsurgicallyimplantedtransmitters(radiofrequencies373and482)(ReinertandCundall1982,Reinert1992,hardyandGreene2000),relocatedtothesamesiteasthesnakesrelocatedbyWalkeretal.(2009),andsubsequentlytracked.on6July,twoadditionalC. horridus(amaleandafemale)werecapturedtogetherinahomeowner’syard,~1.2kmfromthelenexadensite,tangledtogetherinlandscapingfabric.theyweredisentangled,implantedwithtransmitters(radiofrequen-cies105and515,respectively;Fig.1;table1),relocatedtothereleasesiteofWalkeretal.2009,andtracked.Allthreefemalescontainedenlargedfollicles,withfour,seven,andeightfollicles,respectively.likeothersnakesmonitoredbyWalkeretal(2009),thetwo22-Aprilsnakesdispersedinapatternthatreflectedinitialdispersalandhabitatuseofsnakesreleaseddur-ingthemainstudy(Walkeretal.2009;Fig.2). thetwo6-Julysnakes,however,exhibitedbehaviorthatweperceiveaspeculiarforthespecies(Fig.2).Ratherthandispersingfromtheirreleasesiteandeachother,bothstayedwithin~300mofthereleasesite(therelo-cation-hibernaculum)fortheremainderoftheseason(2½months),withtheexceptionofashortforaybythemaletoasite~825mstraightlinedis-tanceawayfor2½weeks(29Augustthroughmid-september;Fig.3).hesubsequentlyreturnedtothepair’sreleasesitenearthedenandwasfoundnexttothefemaleon19september.Duringtheirtimeintheprairieneartheden,thetwooftenwerelocatedtogetherornearoneanother. thematingsystemofC. horridushasbeendescribedasprolongedmate-searchpolygyny(brown1995),asysteminwhichmalesout-competeoneanotherintheireffortstofind,court,andcopulatewithspatiallydis-persedfemalesduringaprolonged,late-summermatingseason(Duvalletal.

1992).thecourtshipperioditselfmaygoonforweeks,andmaleshavebeenobservedaccompanyingfemalesforupto15consecutivedays(mcGowanandmadison2008).however,malestypicallyendthiscourtshipperiodoncetheyhavecopulated,aredisplacedbyanothermale,orloseinterestinthefemale(mcGowanandmadison2008).themaleinthisstudywaspairedwiththefemaleuponcapture(6July)andthroughtheactiveseasonuntilbothingressedon27september,foratotalofsixweeksofpairing. In2010,followingsuccessfulhibernationandegressfromtherelo-cation-sitehibernaculum,thepairdiverged.onceseparated,bothsnakesindependentlyexhibitedanaffinityforanthropogenicstructures.thefemaleremainedintheyardofanearbyhomeowner,andwasfoundbeneaththeporchofthehomemultipletimesthroughouttheseason;wemovedtheanimal~100minresponsetohomeownerrequests,butthesnakesoonreturned.sheeventuallyhadtobere-relocatedtoanotherpopulation40kmwestinordertoplacatethehomeownerandassurethesafetyofthesnake.themalespentthemajorityoftheseasononthegroundsofanearbypublicfacility,theninadifferenthomeowner’syard,andfinallyinthevicin-ityofmaintenanceshedsonprivateproperty.heultimatelyingressedatanextensiveanthropogenicrock-rubblepilejustbehindoneofthemaintenancebuildingsratherthanreturningtotherelocation-hibernaculum.nootherrattlesnakeshavebeenobservedorreportedfromthisrubblepile. thismaleandfemalewerefound~1.2kmfromtheindividualscol-lectedattheoriginaldensite.theymighthavebeenpartofadifferentorig-inal-denpopulation;notalldensinthelenexaoutskirtshavebeenmapped,andseveralpotentiallocationsexist.thiscouldexplainmuchoftheirasso-ciativebehavior,asdenmatesbelongtothesamesocialsystem,arelikelytobemorecloselyrelatedand“familiar”tooneanotherthantheyaretoindi-vidualsfromanotherden,andarethoughttoexhibitkinrecognitionbehav-ior(Clark2004).moreover,theareaoftherelocationsiteinwhichthesetwojointlyspentthefirststudyseason(2009)containedabundantrodenttrails(Walker,unpubl.data),sopreywaslikelyabundant,makingexten-siveforagingunnecessary.similarly,preywasplentifulnearthemanmadestructureswhereeachofthetwosnakesspentthe2010season(Walker,pers.obs).specifically,theporchunderwhichthefemalesettledwaswithinafewmetersofabirdfeeder,andfeatherrachiseswerefoundinsnakescatbeneaththeporch.DuringoneoutingweobservedalargeCopperhead(Agkistrodon contortrix)inthesameflowerbedwithinameterofthefemaleC. horridus. Inseptember2007,GRpaccompaniedW.s.browntoanislandinlakeGeorge,newYork,onwhichaC. horridusdenwaslocated.twopeo-pleresidentontheislandoftenobservedrattlesnakesintheiryard,andwhenGRpaskedwhere,theyunhesitatinglyreplied“underthebirdfeeders.”theyhadobservedthatseeddislodgedfromtheseveralfeedersbybirdsattractedabundantresidentchipmunks,andthese—perhapswithanoccasionalbird

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Fig. 2. Aerialviewofthereleasesite(¶)andassociatedhabitats(3,648ft=1,112m).eachsnake’speriodiclocation(pertelemetry)andhabitatuse(2009season)isindicatedbyadifferentcolor.

Fig. 3.maximumdispersaldistance(m)traveledbyeachtelemeteredindividualduringthe2009activeseason.

Table 1.FourtimberRattlesnakes(Crotalus horridus)relocatedanddis-cussedinthispaper.

Frequency Sex Initial SVL Tail Release Mortality Mass (cm) Length Date (g) (cm)

373 ♀(gravid) 435 82.2 5.5 4may2009 Yes*

482 ♀(gravid) 543 85.3 5.5 4may2009 no

515 ♀(gravid) 825 99.0 7.0 16July2009 no

105 ♂ 960 97.0 8.7 16July2009 no

*Causeunknown.

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—werearichfoodresourcefortherattlesnakes.sajdakandbartz(2004)reportedpredationbyC. horridusonaYellow-belliedsapsucker(Sphyrapicus varius)inaresidentialyard.brown(1993)citedobservationsthataddition-allyindicatetheadaptabilityofC. horridustohumanpresenceandactivity,althoughthiscanfrequentlyresultinmortalityforthesnakes. kapferetal.(2010)indicatedtheimportanceoftheratioofsuit-abletounsuitablehabitatinassessingthehome-rangesizeofalargesnakespecies.Anindividual’shomerangeisdeterminedbytheareatheanimalmusttraversetosuccessfullymeetitsenergeticneedsandencountersuitablepotentialmates.presumably,ifanyindividualC. horridus —aspeciesthatemploysa“sitandwait”foragingstrategy—couldmeetitsforagingneedswithinaverysmalltract,itwouldhaveincentivetoremainthere,especiallyifitwasafemaleandnotdrivenbymate-seekingbehavior.beaupre(2008)observedbehavioraldifferencesofC. horridusinprey-richandprey-poornaturalconditions.Additionally,C. horridusispotentiallylong-lived(W.s.brown,pers.comm.;Fitchandpisani2002)andmightbecapableofrapidassociativelearningwhenstimulihavehighsurvivalvalue(seediscussioninAbramsonandplace2008). takentogetherandappliedtotheforagingbehavioroffemale-515andmale-105,theseobservationssuggestthatadultC. horridusmightbebehaviorallyaswellasphenotypicallyplastic(e.g.,Jenkinsetal.2009),andthatsomeindividualsmightbeverytolerantof(orevenshowaffinityfor)nearbyhumanactivity(Fig.4)anddisturbanceifabundantpreyareassoci-atedwithanthropogenichabitats(gardens,buildings,etc.).Unfortunately,thistoleranceisseldomextendedinreverse.AlthoughastrongaffinityforbuildingsisatypicaloftimberRattlesnakesgenerally,giventheirwide-spreadgeographicoverlapwithhumans(brown1993,Walkeretal.2009),theircrypticandgenerallysecretivenature(brown1993,Furman2007),

andthecopiousnumbersofpotentialpreyattractedtovariousanthropo-genicstructures,thatmoresnakesfromtherelocation-hibernaculumdidnotemulatethesetwoanimalsandforagesimilarlynearanthropogenicstructuresisperhapssurprising.

AcknowledgementsJenniferDorrandlenexaAnimalControlofficersinitiallycapturedthesnakes;lindalehrbaum,CodyVanDyke,andCaitlynmcCallhelpedwithtracking;andtwoanonymousreviewersmadehelpfulcommentsthatimprovedthisreport.

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Fig. 4.sometimberRattlesnakes(Crotalus horridus)demonstrateanapparentaffin-ityforanthropogenichabitats.thismalewasfoundbeneathaconstructionsign.

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